1. Field of the Invention
The invention pertains to the field of beverage dispensers. More particularly, the invention pertains to hot beverage dispensers using liquid concentrate or materials from which beverages are extracted by hot water.
2. Description of Related Art
Embodiments of the invention described below include liquid concentrate and brewing machines for hot beverages, particularly coffee.
Basically all commercial coffee brewers operate in the same way, where the difference between one brand to the other is in added features and look. The brewers have a water heating tank of 1-2 gallons with high power heating elements of 4-7 kw. They fill the tank with water and heat the water to the brewing temp. which is between 180-190° F. The hot water is pushed out by the increased thermal pressure or by gravity into the spraying head which sprays hot water on the ground coffee beans.
This method suffers from numerous disadvantages which result in an imperfect brewing.    A. Optimal brewing temperature for coffee is 200-205° F. In the current brewing method they cannot brew above 180-190° F. since the resulting coffee becomes dangerous to consume. Drinking hot beverages at temperature above 180° F. can cause serious mouth burns.    B. The brewing time for 1 to 2 gallons of coffee is of the order of 10 to 15 minutes, which is too long for optimal extraction. Long extraction time degrades the quality and taste of the brewed coffee.    C. Nonuniform extraction due to nonuniform flow of the hot water through the granular coffee bed. This effect is referred to as “channeling”—the hot water creates channels through the ground coffee.    D. Inefficient extraction which results in low soluble and flavor yield.    E. In order to be ready for the next brewing the brewer operator will fill it with water and keep the water at brewing temperature (180-190° F.) until the next brewing batch, which might be few minutes or few hours. When the hot water is sitting in the water tank for long period of time it depletes its Oxygen and mineral which degrades the water and therefore the coffee taste.    D. Over time, the deposition of water minerals on the tank walls and heating elements builds layers of “stone” which degrades the brewer performance and shortens its useful life time.
In the trade, coffee in liquid concentrate form is often called “Liquid Coffee”. The terms “liquid beverage concentrate” and “liquid coffee” are used interchangeably in this application. It will be understood that these terms could also apply to other liquid concentrate beverages, such as hot chocolate, espresso, cappuccino, mulled cider, etc.
Beverage dispensers using liquid beverage concentrate, which is mixed with hot water to dispense hot coffee or chocolate or the like are known to the art. U.S. Pat. No. 3,634,107, “Apparatus for Dispensing Coffee Beverage” is an example of one such device.
In prior art liquid coffee dispensers, the hot water to be mixed with the concentrate is held in large (typically 4-6 gallon) tanks maintained at high temperature. Water is fed by gravity from the tank, and is mixed with liquid coffee concentrate at or near the dispensing spigot. Incomplete mixing often leads to “stripes” of dark concentrate and clear water leaving the spigot, with the beverage variably and incompletely mixing in the cup.
Hot water drawn out made up by incoming tap water at low temperature, so that the temperature in the tank varies as the dispenser is used—the more coffee dispensed, the lower the temperature, as cool makeup water dilutes the hot water in the tank.
The gravity feed is relatively low in pressure, and this means that it takes the water flow a longer time to reach flow equilibrium, during which time the ratio of concentrate to water varies considerably from the desired ratio. This results in an inconsistent coffee taste.
As the hot water is held, entrained oxygen escapes, and minerals in the water deposit on the walls of the tank and heating elements, leaving the water “flat”. The flat water does not release as much aroma from the concentrate as would be desirable and the dispensed beverage does not have the desired flavor. The deposited minerals flake off the tank walls, putting occasional flakes of mineral in the cup and giving an “off” taste to the beverage.
Keeping a beverage dispensing system clean is a key to good-tasting beverages, yet prior art machines are not designed to promote easy and regular cleaning.
Such machines are supposed to have a daily cleaning, where plain water is run through the mix section (only) of the machine. Weekly, the containers of concentrate should be removed and replaced with a bag of water and sanitizing chemical, to clean the product dispensing part of the machine. In practice, neither is done, and the beverage and other contaminants build up on the walls of the tubing, imparting an “off” flavor to the dispensed beverage. At worst there is a possibility of growth of bacteria or other harmful organisms in the tubing and dispensing areas.